Molecular mechanism of membrane protein integration into the endoplasmic reticulum

Article Abstract:

The molecular mechanisms that mediate the integration of proteins with two transmembrane (TM) domains into the endoplasmic reticulum were analyzed to characterize ribosome-membrane interactions. Analysis of the integration of membrane proteins with two TM sequences into mammalian microsomes indicated the presence of continuous membrane binding during ribosome synthesis. Furthermore, the lumenal and cytoplasmic domains of the membrane protein were synthesized in the membrane-bound ribosome while the TM sequences were released into the lipid phase during membrane integration.

Biological transport, Active, Active biological transport, Ribosomes

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Signal sequence recognition in posttranslational protein transport across the yeast ER membrane

Article Abstract:

The signal sequence of prepro-alpha-factor interacts in a Kar2p- and ATP-independent reaction with Sec61p, the multispanning membrane component of the protein-conducting channel. The signal sequence is recognized during the first step of its posttranslational transport across the yeast endoplasmic reticulum membrane. Interaction needs a functional signal sequence and an intact Sec complex, but not Kar2p or ATP. Upon binding to the Sec complex, the signal sequence contacts mainly Sec61p.

Proteins, Protein synthesis

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The Sec61p complex mediates the integration of a membrane protein by allowing lipid partitioning of the transmembrane domain

Article Abstract:

Results demonstrate that the translocation site protein Sec61p directs the transmembrane domain of a membrane protein to the interface channel and lipid. Data further show that the hydrophobicity and the length of the TM domain determines its localization and eventual tethering to the ribosome.

United States, Switzerland, Physiological aspects, Biological transport, Lipid membranes, Bilayer lipid membranes

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